Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2003-03-04
2004-03-16
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S265000
Reexamination Certificate
active
06706825
ABSTRACT:
TECHNICAL FIELD
This invention relates to aromatic polycarbonate base resin compositions having improved flame retardance and articles made through molding thereof.
BACKGROUND OF THE INVENTION
Due to excellent mechanical, electrical and thermal properties, molded parts of aromatic polycarbonate resins have been commonly used as engineering plastics in a wide variety of applications including business machine, electric and electronic, automobile and building fields. To overcome the drawbacks of aromatic polycarbonate resins including somewhat poor processability and moldability, a number of polymer blends with other thermoplastic resins such as polystyrene resins, acrylonitrile-butadiene-styrene (ABS) resins, and polyester resins have been developed. Among others, polymer alloys with ABS resins have been widely used in automobile, business machine and electric and electronic fields.
In the current applications including business machines, electric appliances and the like, it is strongly desired to render the resin materials flame retardant. To meet such needs, numerous flame retarding techniques have been proposed for aromatic polycarbonate resins and polymer alloys thereof with other thermoplastic resins.
In the prior art, for rendering aromatic polycarbonate resins and polymer alloys thereof flame retardant, it was a common practice to use an organic halide flame retardant containing bromine in combination with a flame retardant aid such as antimony trioxide as disclosed in JP-A 64-22958. Resin compositions of this formulation are made flame retardant to a relatively large extent, but raise environmental problems of giving off harmful or toxic substances during fire occurrence or combustion upon disposal by incineration. In addition, the production of molded parts from such resin compositions has the problem that if thermally decomposed, the flame retardant gives off hydrogen halide which can cause corrosion of molds or detract from physical properties of molded resin parts themselves. For this reason, efforts were made on the technique of achieving flame retardance without resorting to organic halide compounds containing bromine.
For example, attempts were made to use phosphate esters in combination with polytetrafluoroethylene having a fibrillating ability. JP-A 61-55145 describes an anti-fouling thermoplastic molding composition comprising an aromatic polycarbonate resin, ABS resin, AS resin, halide, phosphate and polytetrafluoroethylene. JP-A 2-32154 describes a flame retardant, high impact polycarbonate molding composition comprising an aromatic polycarbonate resin, ABS resin, AS resin, phosphate and polytetrafluoroethylene. It is disclosed in these patents that in addition to the foregoing components, stabilizers, pigments, flow aids, fillers, reinforcements, mold release agents and/or antistatic agents may be included in the compositions. JP-A 2-69557 describes a flame retardant, thermoplastic polycarbonate molding composition comprising an aromatic polycarbonate resin, ABS resin, AS resin, specific phosphate and polytetrafluoroethylene. JP-A 2-115262 describes a flame retardant composition comprising an aromatic polycarbonate resin, ABS resin, and oligomeric phosphate. These flame retarding formulations predominantly using phosphates suffer from several problems including the heavy loading of flame retardants and the volatility of phosphates which leads to poor heat resistance or causes mold contamination.
By contrast, silicone resins have high heat resistance, give off no toxic gases upon combustion, and are safe in themselves. Silicone resins of several types have been proposed as the flame retardant for polycarbonate resins. In fact, silicone resins are used as the flame retardant in resin compositions of which business machine parts are made.
U.S. Pat. No. 4,387,176 (Frye), JP-A 4-226159 and JP-A 7-33971 describe flame retardant resin compositions to which silicone resins comprising monofunctional siloxane units and tetrafunctional siloxane units are added. JP-A 54-36365 describes a flame retardant composition to which a substantially solid silicone resin containing at least 80% by weight of trifunctional siloxane units is added. JP-A 10-139964 and JP-A 11-140294 describe flame retardant compositions to which a substantially solid silicone resin comprising di- and trifunctional siloxane units, having a relatively high molecular weight and bearing phenyl groups is added. Allegedly, these silicone resins having branched structures offer improved heat resistance, and the silicone resin bearing phenyl groups exerts flame retardant effects by forming an incombustible Si—C ceramic layer through mutual coupling of aromatic rings on the surface of the resin to which it is added.
Also, JP-A 54-102352 describes a thermoplastic resin composition comprising an aromatic polycarbonate resin and a silicone oligomer containing poly-substituted ethoxy groups; JP-A 6-306265 describes a flame retardant polycarbonate resin composition comprising as essential components an aromatic polycarbonate resin, an alkali (or alkaline earth) metal salt of perfluoroalkanesulfonic acid, and an organic siloxane having alkoxy, vinyl and phenyl groups; JP-A 6-336547 describes a flame retardant polycarbonate resin composition comprising an aromatic polycarbonate resin, an alkali (or alkaline earth) metal salt of perfluoroalkanesulfonic acid, and an organopolysiloxane containing organooxysilyl groups each bonded to a silicon atom through a divalent hydrocarbon group; and JP-A 11-222559 and JP-A 2000-226527 describe a flame retardant composition comprising a synthetic resin containing aromatic rings in a molecule and an organopolysiloxane containing phenyl and alkoxy groups. It is believed that when these resin compositions are burned, organopolysiloxane molecules or an organopolysiloxane and a resin component are joined through oxidative decomposition and crosslinking of alkoxy or organooxy groups, to form a network structure which is fixed in proximity to the burning portion, thus exerting flame retardant effects.
Silicone compounds of other types are also employed. JP-A 51-45160 describes an organopolysiloxane containing Si—H groups; JP-A 6-128434 describes an organopolysiloxane resin comprising vinyl group-bearing siloxane units; JP-A 8-176425 describes an organopolysiloxane containing epoxy groups; and JP-A 8-176427 describes a polycarbonate resin modified with a phenolic hydroxyl group-bearing organopolysiloxane.
Attempts have also been made to add various silicone resins to polymer alloys of aromatic polycarbonate resins with other thermoplastic resins. JP-A 62-297352 describes to blend silicone rubber for improving chemical resistance, weather resistance and heat resistance. JP-A 7-126510 describes that impact resistance can be improved by including a composite rubber of the structure in which a polyorganosiloxane rubber component and a polyalkyl (meth)acrylate rubber component are entangled together in an inseparable manner.
Likewise, it has been proposed to add silicone resins to such polymer alloys for the purpose of improving flame retardance. JP-A 4-298554 describes the addition of a phosphate ester and a polyorganosiloxane, and illustrates the use of polymethylphenylsiloxane and low density polyethylene-modified polysiloxanes in Examples. Additionally, JP-A 5-179123 describes a flame retardant composition based on a phosphorus compound and a boron compound to which a polyorganosiloxane and/or a fluoro-resin is added; JP-A 8-165392 describes the combined use of a phosphate flame retardant and an organohydrogenpolysiloxane; and JP-A 10-147702 describes the combined use of a phosphate flame retardant and a polyorganosiloxane graft copolymer.
In all the flame retardant compositions described above, however, silicone flame retardants are essentially used as co-agents to be combined with phosphate flame retardants. None of the foregoing silicone flame retardants can render polymer alloys flame retardant when used alone.
In the fields of business machines, electric appliances and the like, ther
Itagaki Akinari
Yamaya Masaaki
Moore Margaret G.
Shin-Etsu Chemical Co. , Ltd.
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